http://www.rfc-editor.org/rfc/rfc7234.txt
RFC 7234: Hypertext Transfer Protocol (HTTP/1.1): Caching, R. Fielding, M. Nottingham, J. Reschke2014-06-01T23:00:00-00:00The Hypertext Transfer Protocol (HTTP) is a stateless \%application- level protocol for distributed, collaborative, hypertext information systems. This document defines HTTP caches and the associated header fields that control cache behavior or indicate cacheable response messages.